[Technical Field]
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The present invention relates to a light source lamp and a projector.
[Background Art]
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Generally, a light source lamp of a projector includes a light emitting tube, and a
reflector which reflects light from this light emitting tube and emits this light to an
illuminated region side as illumination light. Further, as this type of light source lamp, a
lamp having an auxiliary mirror which are arranged on the illuminated region side and
reflects light from a light emitting tube onto the reflector has been also known (refer to,
for example, Patent Reference 1).
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According to such the light source lamp, stray light of the light from the light
emitting tube, which is not adapted for use, can be effectively utilized. Further, it is not
necessary to set the size of the reflector to such size as to cover the illuminated-region-sided
end part, so that the size of the reflector can be reduced, and the size of the projector
can be reduced.
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[Patent Reference 1] JP-A-8-31382 (Fig. 1)
[Disclosure of the Invention]
[Problems that the Invention is to Solve]
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However, with recent increase of luminance of the projector, the inside of the light
emitting tube composed of high pressure mercury-vapor lamp is in a very high-pressure
state (for example, 200 Pascal and more). Therefore, in the light emitting tube, in order to
resist this air pressure, quartz glass constituting a bulb of the light emitting tube has been
made thick and a seal type referred to as shrink seal has been adopted. In result, though
high output from the light emitting tube can be obtained, there is a problem that light
utilizing efficiency lowers.
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Fig. 6 is a diagram for explaining a light source lamp having such the high
luminance. Fig. 6A is a partially enlarged view showing the sectional structure of the
light source lamp, and Fig. 6B is a diagram in which a light ray is shown in Fig. 6A. In
the Figs. 6A and 6B, a reflector is omitted.
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In a tube bulb of a light emitting tube 912 used in this light source lamp, as shown
in Fig. 6A, parts distant from attachment portions of electrodes 905, 906 are thicker than
parts close to the attachment portions. Therefore, as shown in Fig. 6B, of the radiation
light from the light emitting tube 912, the light reflected on a reflection concave surface
916is of an auxiliary mirror 916 does not run toward a center Q of curvature (i.e., center P
of the luminous part (middle point of a line connecting a pair of electrodes 905 and 906))
of the reflection concave surface 916is, and shifts to the reflector side (side opposite to an
illuminated region side of the auxiliary mirror 916) due to the lens effect of the tube bulb
of the light emitting tube.
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Therefore, since such the light does not pass near a focus (in case of an ellipsoidal
reflector, near a first focus of the ellipsoidal reflector; in case of a paraboloidal reflector,
near a focus of the paraboloidal reflector), quality of the illumination light lowers (in case
of the ellipsoidal reflector, light collecting property lowers; and in case of the paraboloidal
reflector, a parallel level lowers), so that the available amount of illumination light on the
illuminated region side is reduced, and light utilizing efficiency lowers. Further, such the
light may collide with the electrode 905 on the reflector side. In this case, also, the
available amount of illumination light on the illuminated region side is reduced, and light
utilizing efficiency lowers. The conventional light source lamp had such the problems.
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Therefore, the invention has been made in order to solve the above problems, and
its object is to provide a light source lamp and a projector in which reduction of the
available amount of illumination light on the illuminated region side can be suppressed
thereby to heighten the light utilizing efficiency.
[Means for Solving the Problems]
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A light source lamp of the invention, which includes a light emitting tube having a
luminous part in which a pair of electrodes arranged along an illumination light axis are
built, a reflector which reflects the light from the luminous part and emits its light as
illumination light to an illuminated region side, and an auxiliary mirror which is arranged
on the illuminated region side of the luminous part, has a reflection concave surface of a
nearly hemispherical shape, and reflects the light from the luminous part on the reflector,
is characterized in that a center of curvature of the auxiliary mirror is arranged in a
position distant from a luminous center of the luminous part to the illuminated region side
along the illumination light axis.
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Therefore, according to the light source lamp of the invention, a luminous flux
which is radiated from the luminous center of the luminous part of the light emitting tube
and runs toward the auxiliary mirror, even if after it has refracted on the inner surface and
the outer surface of a tube bulb of the luminous part and emitted from the luminous part, it
is reflected by the auxiliary mirror and refracted again on the inner surface and the outer
surface of the luminous part, can be returned near the luminous center of the luminous
part. Namely, of the radiation light from the light emitting tube, the light reflected on the
reflection concave surface of the auxiliary mirror, without colliding with the electrode on
the reflector side, passes near a focus of the reflector (in case of an ellipsoidal reflector,
near a first focus of the ellipsoidal reflector; in case of a paraboloidal reflector, near a
focus of the paraboloidal reflector), and is emitted toward the reflector. The luminous
flux reflected by the auxiliary mirror, similarly to the light that is directly incident from
the luminous center of the luminous part onto the reflector, can be incident onto the
reflector. Therefore, loss of light radiated from the light emitting tube can be prevented,
and decrease of quality of the illumination light is suppressed as much as possible, so that
reduction of the available amount of illumination light on the illuminated region side is
suppressed, and light utilizing efficiency can be improved.
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In the light source lamp of the invention, it is preferable that the dimension d
between a center of the luminous part and a center of curvature of the auxiliary mirror is
set to the dimension satisfying the following inequality: 0.0081 × D ≤ d ≤ 0.048 × D,
wherein D is a radius of curvature of the reflection concave surface.
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By such the constitution, as shown in embodiments described later, reduction of
the available amount of illumination light on the illuminated region side is effectively
suppressed, and the light utilizing efficiency can be effectively improved.
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In the light source lamp of the invention, it is preferable that: the reflector is an
ellipsoidal reflector which emits the luminous flux emitted from a first focus position as a
luminous flux converging toward a second focus position; and the first focus of the
ellipsoidal reflector coincides nearly with the luminous center of the luminous part.
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In the light source lamp of the invention, it is preferable that: the reflector is
alternatively a paraboloidal reflector which emits the luminous flux emitted from a focus
position as light parallel to the illumination light axis; and the focus position of the
paraboloidal reflector coincides nearly with the luminous center of the luminous part.
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According to the light source lamp of the invention, in any type of reflector, the
light utilizing efficiency can be improved.
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A projector of the invention, which includes an illumination device having a light
source lamp which emits illumination light to an illuminated region side, an electro-optic
modulator which modulates the illumination light emitted from the illumination device
according to image data, and a projection lens which projects the light modulated by the
electro-optic modulator, is characterized in that the light source lamp is any one of the
above-described light source lamps.
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Therefore, since the projector of the invention includes the superior light source
lamp which can improve the light utilizing efficiency effectively, it has higher luminance.
[Brief Description of the Drawings]
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- [Fig. 1] It is a diagram showing an optical system of a projector according to a
first embodiment.
- [Fig. 2] It is a sectional view showing a light source lamp according to the first
embodiment.
- [Fig. 3] It is a diagram for explaining an effect of the light source lamp according
to the first embodiment.
- [Fig. 4] It is a diagram for explaining the effect of the light source lamp according
to the first embodiment.
- [Fig. 5] It is a diagram showing an optical system of a projector according to a
second embodiment.
- [Fig. 6] It is a diagram for explaining a problem of a conventional light source
lamp.
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[Best Mode for Carrying Out the Invention]
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A light source lamp and a projector to which the invention is applied will be
described below with reference to embodiments shown in figures.
[Embodiment 1]
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Firstly, a projector according to a first embodiment of the invention will be
described with reference to Fig. 1.
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Fig. 1 is a diagram showing an optical system of a projector according to the first
embodiment of the invention. In the following description, three directions orthogonal to
one another are respectively taken as a z-direction (direction of an illumination light axis
110Aax in Fig. 1), an x-direction (direction parallel to a paper surface in Fig. 1 and
orthogonal to the z-axis), and a y-direction (direction perpendicular to the paper surface in
Fig. 1 and orthogonal to the z-axis).
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A projector 1000A according to the embodiment of the invention, as shown in Fig.
1, includes an illumination device 100A, a liquid crystal display device 400 as an electro-optic
modulator, and a projection lens 600.
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The illumination device 100A includes a light source lamp 110A, an integrator rod
120, and a relay optical system 140. Between the light source lamp 110A and the
integrator rod 120, an infrared mirror 118 is arranged.
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Fig. 2 is a sectional view showing the light source lamp according to the first
embodiment.
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The light source lamp 110A, as shown in Figs. 1 and 2, includes a light emitting
tube 112, an ellipsoidal reflector 114A, and an auxiliary mirror 116.
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The light emitting tube 112 comprises a luminous part 2 in which a pair of
tungsten-made electrodes 5 and 6 arranged along the illumination light axis 110Aax are
built, and seal parts 3, 4 coupling to the front and back (both side parts in Fig. 2) of the
luminous part 2. The whole of the light emitting tube 112 is formed by a tube member
made of quartz glass. The luminous part 2 is composed of a hollow spherical body, and
seals mercury, rare gas, and halogen therein.
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As the light emitting tube 112, various light emitting tubes which emit high-intensity
light can be adopted, for example, a metal haloid lamp, a high pressure mercury-vapor
lamp, and a super high pressure mercury-vapor lamp.
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Further, the luminous part 2 is arranged near a first focus position on the ellipsoidal
reflector side, of two focuses (first focus and second focus) of the ellipsoidal reflector
114A. The ellipsoidal reflector 114A collects the luminous flux emitted from the first
focus position on the second focus position. In the seal parts 3, 4, metal foils respectively
connecting to the electrodes 5, 6 are sealed. To the metal foils, lead wires for external
connection are connected respectively.
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When the voltage is applied to the lead wires, potential difference is produced
through the metal foils between the electrodes 5 and 6, and discharge is produced, so that
an arc image is generated and the luminous part 2 emits light.
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Further, on the peripheral surface of the luminous part 2, antireflection coating of a
multi-layered film including a tantalum oxide film, a hafnium oxide film, and a titanium
oxide film is applied, whereby optical loss due to reflection of the light passing through
the peripheral surface can be reduced.
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The ellipsoidal reflector 114A, as shown in Fig. 2, has the two focuses (first focus
and second focus) located on the illumination light axis 110Aax; and includes a rotary
ellipsoidal reflection part which reflects the light from the luminous part 2 thereby to emit
its light to the illuminated region side as illumination light, and a sleeve-shaped neck part
having a through-hole into which the seal part 3 of the light emitting tube 112 is inserted
and fixed. The through-hole of the neck part is arranged along a center axis (illumination
light axis 110Aax) of the rotary ellipsoidal surface of the reflection part of the ellipsoidal
reflector 114A. Into the through-hole of the neck part, the seal part 3 of the light emitting
tube 112 is fixed with inorganic adhesive such as cement.
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The reflection part of the ellipsoidal reflector 114A has a reflection surface formed
by evaporating a metal thin film on the rotary ellipsoidal glass surface, and this reflection
surface functions as a cold mirror which reflects visible light and transmits infrared rays.
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Such the ellipsoidal reflector 114A, when the light emitting tube 112 is lightened,
reflects the luminous flux radiated from the luminous part 2 on the reflection surface, and
emits convergent light which converges in the second focus position of the rotary
ellipsoidal surface.
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The auxiliary mirror 116 is arranged on the illuminated region side of the luminous
part 2 so as to be opposed to the ellipsoidal reflector 114A with the luminous part 2
between, and reflects the light from the luminous part 2 toward the luminous part 2,
whereby its reflection light is incident onto the ellipsoidal reflector 114A. The auxiliary
mirror 116 includes a through-hole for auxiliary mirror attachment, which perforates in
the direction of the illumination light axis 110Aax, and into which the seal part 4 of the
light emitting tube 112 is inserted and fixed; and a concave mirror having such a
reflection concave surface 116is of a nearly hemispherical shape as to cover the
illuminated-region-sided surface of the luminous part 2. For example, radius D of
curvature of the reflection concave surface 116is is set to a dimension of D = 6.2 mm. The
auxiliary mirror 116 is fixed on the seal part 4 with inorganic adhesive 8 such as cement.
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The auxiliary mirror 116 is formed of inorganic material such as quartz glass, light-transmissive
alumina, sapphire, or ruby. On the reflection concave surface 116is of the
auxiliary mirror 116, a reflection layer is formed by evaporating metal, and this reflection
layer functions as a cold mirror which reflects visible light similarly to the reflection
surface of the ellipsoidal reflector 114A and transmits infrared rays and ultraviolet rays.
Hereby, in use of the projector, the infrared rays pass through the auxiliary mirror 116
thereby to suppress the increase of temperature of the auxiliary mirror 116, and the
reflected light from the light emitting tube 112 is effectively utilized.
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As the reflection layer of the reflection concave surface 116is, a dielectric multilayer
film is formed by laminating a Ta2O5 film and a SiO2 film alternately. Hereby, in
use of the projector, the infrared rays pass through the auxiliary mirror 116 thereby to
suppress the increase of temperature of the auxiliary mirror 116, and the reflected light by
the auxiliary mirror 116 is effectively utilized.
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By attaching the auxiliary mirror 116 to the light emitting tube 112, the luminous
flux radiated to the opposite side (illuminated region side) to the side on which the
ellipsoidal reflector 114A is arranged, of the luminous fluxes radiated from the luminous
part 2, is reflected to the ellipsoidal reflector 114A side by the reflection concave surface
116is of this auxiliary mirror 116, and further reflected on the reflection surface of the
ellipsoidal reflector 114A, so that its reflection light is emitted from the reflection part of
the ellipsoidal reflector 114A and emitted so as to converge toward the second focus
position.
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As described above, by using such the auxiliary mirror 116, the luminous flux
radiated from the luminous part 2 to the opposite side (front side) to the ellipsoidal
reflector 114A side can be converged in the second focus position of the ellipsoidal
reflector 114A similarly to the luminous flux that is incident directly onto the reflection
surface of the ellipsoidal reflector 114A from the luminous part 2.
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In the conventional light source lamp having no auxiliary mirror 116, since the
luminous flux emitted from the light emitting tube must be converged in the second focus
position by only the ellipsoidal reflector, the reflection part of the ellipsoidal reflector
must be widened.
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However, by providing the auxiliary mirror 116, the luminous flux radiated from
the luminous part 2 to the opposite side (illuminated region side) to the ellipsoidal
reflector 114A side can be reflected on the ellipsoidal reflector 114A side by the auxiliary
mirror 116 so as to be incident on the reflection surface of the ellipsoidal reflector 114A.
Therefore, even in case that the reflection part of the ellipsoidal reflector 114A is small,
almost all of the luminous fluxes emitted from the luminous part 2 can be emitted so as to
converge in the fixed position, so that the dimension in direction of the illumination light
axis 110Aax of the ellipsoidal reflector 114A and its opening diameter can be made small.
Namely, the light source lamp 110A and the projector 1000A can be miniaturized, and
layout for building the light source lamp 110A into the projector 1000A is also facilitated.
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Further, by providing the auxiliary mirror 116 in order to make a light collective
spot diameter at the second focus small, even in case that the first focus of the ellipsoidal
reflector 114A and the second focus thereof are brought close to each other, almost all of
the light radiated from the luminous part 2 is collected at the second focus by the
ellipsoidal reflector 114A and the auxiliary mirror 116 and becomes available, so that the
light utilizing efficiency can be improved greatly. Hereby, a light emitting tube of
comparatively low output can be also adopted, and the temperature of the light emitting
tube 112 and the temperature of the light source lamp 110A can be also lowered.
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Fig. 3 is a diagram for explaining the light source lamp 110A according to the first
embodiment. Fig. 3A is a partially sectional view showing a main portion of the light
source lamp, and Fig. 3B is a diagram in which a light ray is shown in Fig. 3A.
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The auxiliary mirror 116, as shown in Fig. 3A, has the reflection concave surface
116is of the nearly hemispherical shape. A center Q of curvature of the auxiliary mirror
116 is arranged in a position distant, by the predetermined distance, from a center P
(middle point of a line connecting a pair of electrodes 5 and 6) of the luminous part 2
toward the illuminated region side along the illumination light axis 100Aax.
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The luminous flux which is radiated from the luminous center P of the luminous
part 2 and runs toward the auxiliary mirror 116, even if after it is refracted on the inner
surface and the outer surface of the luminous part 2 (by lens effect) and emitted from the
luminous part 2, it reflected by the reflection concave surface 116is of the auxiliary mirror
116 and refracted again on the inner surface and the outer surface of the luminous par 2,
becomes a luminous flux that passes through the luminous center P of the luminous part 2
and is emitted toward the ellipsoidal reflector 114A from the luminous part 2.
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Therefore, according to the light source lamp 110A in the first embodiment, of the
radiation light from the light emitting tube 112, the light reflected on the reflection
concave surface 116is of the auxiliary mirror 116, without colliding with the electrode 5 on
the ellipsoidal reflector side 114A unlike the conventional case, passes near the focus (in
case of an ellipsoidal reflector, near a first focus of the ellipsoidal reflector; and in case of
a paraboloidal reflector, near a focus of the paraboloidal reflector), and can be incident
onto the ellipsoidal reflector 114A similarly to the light running directly to the ellipsoidal
reflector 114A from the luminous part 2. Accordingly, loss of the light emitted from the
luminous part 2 can be prevented, and decrease of quality of the illumination light is
suppressed as much as possible. Therefore, in the light source lamp 110A according to
the first embodiment, reduction of the available amount of illumination light on the
illuminated region side is suppressed, and light-utilizing efficiency can be improved.
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In the light source lamp 110A according to the first embodiment, the dimension d
between a center Q of curvature of the auxiliary mirror 116 and a center P of the luminous
part 2 is set to the dimension satisfying the following inequality: 0.0081 × D ≤ d ≤ 0.048 ×
D, wherein D is a radius of curvature of the reflection concave surface 116is. In this case,
since the radius of curvature D of the auxiliary mirror 116 is, for example, 6.2 mm, the
center Q of curvature thereof is arranged in a position distant from the center P of the
luminous part 2 to the illuminated region side along the illumination light axis 110Aax by
0.05 mm to 0.3 mm (0.05 mm ≤ d ≤ 0.3 mm). Hereby,
the reduction of the available amount of illumination light on the illuminated
region side is suppressed, and the light utilizing efficiency can be effectively improved.
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By the above constitution, according to the light source lamp 110A in the first
embodiment, similarly to the conventional light source lamp, the light emitted from the
light emitting tube 112 to the ellipsoidal reflector 114A side is reflected on the ellipsoidal
reflector 114A and runs toward the illuminated region side. Further, the light emitted to
the illuminated region side of the light emitting tube 112 is reflected by the auxiliary
mirror 116 toward the luminous part 2, and this reflected light is incident in the ellipsoidal
reflector 114A. At this time, the light emitted from the luminous part 2 to the auxiliary
mirror 116 and reflected by the auxiliary mirror 116 toward the luminous part 2, even if it
is refracted on the inner surface and the outer surface of the luminous part 2 (lens effect),
passes the luminous center P of the luminous part 2, that is, near the focus of the
ellipsoidal reflector 114A (in case of the ellipsoidal reflector, near the first focus of the
ellipsoidal reflector; and in case of the paraboloidal reflector, near the focus of the
paraboloidal reflector). Therefore, without losing the light emitted from the luminous part
2, decrease of quality of the illumination light is suppressed as much as possible.
Consequently, in the light source lamp 110A according to the first embodiment, the
reduction of the available amount of illumination light on the illuminated region side is
suppressed, and light-utilizing efficiency can be improved. This effect has been
confirmed by the following experiment.
<Experiment>
[Experiment method]
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- (1) After the auxiliary mirror 116 (the radius D of curvature of the reflection concave
surface 116is is 6.2 mm) was arranged so that the center Q of curvature can be located in
the center P of the luminous part 2, the light emitting tube 112 was lightened, and
transmission efficiency (%) and quantity of light (%) of the illumination light flux
reaching a light incident surface of a liquid crystal display device 400 were measured,
using a measuring device (not shown).
- (2) The auxiliary mirror 116 (the radius D of curvature of the reflection concave
surface 116is is 6.2 mm) was arranged so that the center Q of curvature can be located in a
position distant from the center P of the luminous part 2 to the illuminated region side
along the illumination light axis 110Aax by the dimension d (dimension between the
center Q of curvature of the auxiliary mirror 116 and the center P of the luminous part 2: d
= 13 kinds of 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.35, 0.40
mm). Thereafter, the light emitting tube 112 was lightened, and the transmission
efficiency (%) and the quantity of light (%) of each illumination light flux reaching the
light incident surface of the liquid crystal display device 400 were measured, using a
measuring device (not shown).
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Results of these experiments (1) and (2) are shown in Fig. 4. In Fig. 4, the
measured quantity of light (%) in (2) is represented by the relative quality of light when
the measured quantity of light (%) in (1) is taken as 1 (=100%).
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As clear from Fig. 4, in case that the auxiliary mirror 116 is arranged so that the
center Q of curvature can be located in the position distant from the center P of the
luminous part 2 to the illuminated region side along the illumination light axis 110Aax by
the dimension d (d = 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.35
mm), the reaching quantity of light radiated from the light emitting tube 112 to the
illuminated region side increases (The measured quantity of light is over 100%.)
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Here, in consideration of the measurement error (up to about 1 % of the measured
quantity of light) by the measuring device, 102 % relative quality of light by which the
desired effect can be surely obtained is taken as a threshold value. In case that the above
dimension d satisfies an inequality of 0.05 mm ≤ d ≤ 0.30 mm, it is found that the
reaching quantity of light radiated from the light emitting tube 112 to the illuminated
region side increases.
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Next, the radius D of curvature of the reflection concave surface 116is was changed
from 6.2 mm to 6.0 mm and 6.4 mm, and measurement by the above experiment methods
was executed. In result, it was confirmed also from these measurement results that in
consideration of the measurement error by the measuring device similarly to the case in
the above measurement, the dimensions d by which the desired effect (sure increase of the
reaching quantity of light radiated from the light emitting tube 112 to the illuminated
region side) can be obtained were 0.049 mm ≤ d ≤ 0.29 mm (D=6.0 mm), and 0.05 mm ≤
d ≤ 0.31 mm (D=6.4 mm).
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Accordingly, in the light source lamp 110A according to the first embodiment, the
dimension d (dimension d between the center Q of curvature of the auxiliary mirror 116
and the center P of the luminous part 2) by which the reaching quantity of light radiated
from the light emitting tube 112 to the illuminated region side can be surely increased is
set to the dimension satisfying the following inequality: 0.0081 × D ≤ d ≤ 0.048 × D,
wherein D is the radius of curvature of the reflection concave surface 116is of the auxiliary
mirror 116. Namely, in case that this condition is satisfied, the great reduction of the
available amount of illumination light on the illuminated region side can be suppressed,
and the light utilizing efficiency can be heightened.
[Second embodiment]
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Fig. 5 is a diagram showing an optical system of a projector 1000B according to a
second embodiment of the invention.
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The projector 1000B according to the second embodiment, as shown in Fig. 5, is a
three-plate type projector using three liquid crystal display devices 400R, 400G, and
400B.
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This projector 1000B, as shown in Fig. 5, comprises an illumination device 100B,
a color separation optical system 200, a relay optical system 300, an optical device, and a
projection optical system 600. Optical elements and optical devices constituting these
optical systems 100B to 300 are positioned and housed in a housing for optical parts in
which a predetermined illumination light axis 110Bax is set.
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The illumination device 100B set directions of luminous flux radiated from a
luminous part 2 of a light emitting tube 112 in the fixed direction to illuminate an optical
device 40. The illumination device 100B comprises a light source lamp 110B, a first lens
array 150, a second lens array 160, and a lens integrator optical system having a
polarization converting elements 170 and a superimposing lens 180. Further, the projector
1000B according to the second embodiment uses a paraboloidal reflector 114B as the light
source lamp 110B.
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In the light source lamp 110B, the light emitting tube 112, the paraboloidal
reflector 114B, and an auxiliary mirror 116 are shown schematically. The light source
lamp 110B has a lamp housing for holding these parts, and at a back stage in the luminous
flux emitting direction of the paraboloidal reflector 114B, the integrator optical system is
provided.
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The paraboloidal reflector 114B is attached to the light emitting tube 112 so that its
focus position can nearly coincide with a luminous center P of the luminous part 2. The
luminous fluxes radiated from the luminous center P of the luminous part 2, of which the
emitted directions are set on an illuminated region side of the light source lamp 110B by
the paraboloidal reflector 114B, are emitted to the integrator optical system as light
parallel to the illumination light axis 110Bax.
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The integrator optical system is an optical system which divides the luminous flux
emitted from the light source lamp 110B into plural partial luminous fluxes to unify plane
luminance in the illumination region. This integrator optical system includes a first lens
array 150, a second lens array 160, the polarization converting elements 170 and a
superimposing lens 180.
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The first lens array 150 has a function of a luminous flux dividing optical element
which divides the luminous flux emitted from the light source lamp 110B into plural
partial optical fluxes, and comprises plural small lenses arranged in a matrix manner in a
plane orthogonal to the illumination light axis 110Bax.
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The second lens array 160 is an optical element which collects the plural partial
luminous fluxes divided by the first lens array 150, and comprises plural small lenses
arranged in a matrix manner in a plane orthogonal to the illumination light axis 110Bax
similarly to the first lens array 150.
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The polarization converting elements 170 sets polarization directions of the partial
luminous fluxes divided by the first lens array 150 to linearly polarization in the nearly
same direction.
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This polarization converting elements 170, though shown schematically, comprises
a polarizing separation film and a reflection film which are arranged inclined to the
illumination light axis 100Bax and arranged alternately. The polarizing separation film
transmits one of a P polarization luminous flux and an S polarization luminous flux that
are included in each partial luminous flux, and reflects the other. The other reflected
polarization luminous flux is bent by the reflection film and emitted in the emitting
direction of one polarization luminous flux, that is, in the direction along the illumination
light axis 100Bax. Any of the emitted polarization luminous fluxes is polarization-converted
by a phase plate provided for a luminous flux emitting surface of the
polarization-converting element 170, and the polarization directions of nearly all of the
luminous fluxes are made uniform. By using such the polarization-converting element
170, the luminous fluxes emitted from the light emitting tube 112 can be made the
polarization luminous fluxes in the nearly same direction. Therefore, utilizing efficiency
of the light source light used in the optical device can be improved.
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The superimposing lens 180 is an optical element, which collects the plural partial
luminous fluxes through the first lens array 150, the second lens array 160, and the
polarization converting element 170, and superimposes them on image forming regions of
three liquid crystal display devices of the optical device, which will described later.
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The luminous flux emitted from this superimposing lens 180 is emitted to the color
separation optical system 200.
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The color separation optical system 200 includes two dichroic mirrors 210, 220,
and a reflection mirror 230, and has a function of separating the plural partial luminous
fluxes emitted from the illumination device 100B into three-color light of red (R), green
(G), and blue (B) by the dichroic mirrors 210, 220.
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The dichroic mirror 210, 220 is an optical element having a wavelength selecting
film on a base board, which reflects the luminous flux of the predetermined wavelength
region and transmits the luminous fluxes of other wavelength regions. The dichroic
mirror 210 arranged in the front stage of the light path is a mirror which reflects blue color
light and transmits other color light. Further, the dichroic mirror 220 arranged in the back
stage of the light path is a mirror which reflects green color light and transmits red color
light.
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The relay optical system 300 includes an incident side lens 310, a relay lens 330,
and reflection mirrors 320, 340, and has a function of leading the red color light
transmitted in the dichroic mirror 220 constituting the color separation optical system 200
to the optical device. A reason why such the relay optical system 300 is arranged in the
light path of the red color light is that: since an optical path length of the red color light is
longer than that of another color light, lowering of the light utilizing efficiency due to
divergence of light is prevented. The embodiment, since the optical path length of the red
color light is longer, adopts this constitution. However, by lengthening the optical path
length of the blue color light, the relay optical system 300 may be used for the optical path
length of the blue color light.
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After the blue color light separated by the dichroic mirror 210 has been bent by the
reflection mirror 230, it is supplied to the optical device through a field lens 240B.
Further, the green color light separated by the dichroic mirror 220 is supplied directly to
the optical device through a field lens 240G. Further, the red color light is collected and
bent by the lenses 310, 330 and the reflection mirrors 320, 340 which constitute the relay
optical system 300, and supplied through a field lens 350 to the optical device. Further,
the field lenses 240B, 240G, and 350 are provided in the front stages of the optical paths
of the respective color light of the optical device in order to convert each partial luminous
flux emitted from the second lens array 160 into a telecentric luminous flux for the
illumination light axis 100Bax.
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The optical device modulates the incident luminous flux according to image data
thereby to form a color image. This optical device comprises liquid crystal display
devices 400R, 400G, and 400B (a liquid crystal display device on the red color light side
is taken as 400R, a liquid crystal display device on the green color light side is taken as
400G, and a liquid crystal display device on the blue color light side is taken as 400B.)
functioning as optical modulators that are objects of illumination, and a cross dichroic
prism 500. Further, between each field lens 350, 240G, 240B and each liquid crystal
display device 400R, 400G, 400B, each incident side polarizing plate 918R, 918G, 918B
is interposed. Further, between each liquid crystal display device 400R, 400G, 400B and
the cross-dichroic prism 500, each exit-side polarizing plate 920R, 920G, and 920B are
interposed. By the incident side polarizing plates 918R, 918G, 918B, the liquid crystal
display devices 400R, 400G, 400B, and the exit-side polarizing plates 920R, 920G, and
920B, optical modulation of each color incident light is performed.
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In the liquid crystal display device 400R, 400G, 400B, liquid crystal that is an
electro-optic material is airtightly sealed in a pair of transparent glass substrates. Using a
polysilicon TFT as a switching element, in accordance with the given image signal, the
liquid crystal display device modulates the polarization direction of the polarization
luminous flux emitted from the incident side polarizing plate 44.
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The cross dichroic prism 500 is an optical element, which combines optical images
modulated for the respective color light emitted from the exit-side polarizing plates 920R,
920G, and 920B thereby to form a color image. This cross-dichroic prism 500 is formed
by sticking four right-angle prisms to one another, and it is nearly square-shaped, viewed
in plane. On interfaces in which the right-angle prisms are stuck to one another, dielectric
multilayer films are formed. One 510 R of the nearly X-shaped dielectric multilayer films
reflects the red color light, and the other 510B reflects the blue color light. By these
dielectric multilayer films, the red color light and the blue color light are bent, and their
traveling directions are matched with the traveling direction of the green color light,
whereby the three color light are combined.
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The color image emitted from the cross dichroic prism 500 is enlarged and
projected by the projection optical system 600, and a large image is formed on a screen
SCR.
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The light source lamp 110B is provided with a light emitting tube 112 similar to
that in the first embodiment.
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As described above, the projector 1000B according to the second embodiment is
different from the projector 1000A according to the first embodiment in the number of the
liquid crystal display devices, the kind of integrator optical system, and the kind of
reflector. However, similarly to the case of the projector 1000A according to the first
embodiment, a center of curvature of an auxiliary mirror 116 is arranged in a position
distant from a center of the luminous part to the illuminated region side along the
illumination light axis 100Bax.
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Therefore, also by the light source lamp 110B according to the second
embodiment, the light reflected by the reflection concave surface of the auxiliary mirror
116, of the radiation light from the luminous center P of the luminous part 2 of the light
emitting tube 112, without colliding with the electrode on the paraboloidal reflector 114B
side, runs toward the vicinity of the luminous center P of the luminous part, and passes
near the focus of the paraboloidal reflector 114B (in case of the ellipsoidal reflector, near
the first focus of the ellipsoidal reflector; and in case of the paraboloidal reflector, near the
focus of the paraboloidal reflector). Therefore, without losing the light emitted from the
luminous part 2, decrease of quality of the illumination light is suppressed as much as
possible. Consequently, in the light source lamp 110B according to the second
embodiment, the reduction of the available amount of illumination light on the illuminated
region side is suppressed, and light-utilizing efficiency can be improved.
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The invention is not limited to the above embodiments but various embodiments
can be made without departing from the spirit of the invention. For example, the
following modification can be made.
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Though the illumination device 100A of the projector 1000A according to the first
embodiment uses the light source lamp 110A having the ellipsoidal reflector 114A, it may
use the light source lamp 110B having the paraboloidal reflector 114B in the second
embodiment. However, in case that the illumination device 100A uses the light source
lamp 110B, a collective lens which collects the parallel light emitted from the light source
lamp 110B on an incident part of the integrator rod 120 is provided between the light
source lamp 110B and the integrator rod 120.
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Though the illumination device 100B of the projector 1000B according to the
second embodiment uses the light source lamp 110B having the paraboloidal reflector
114B, it may use the light source lamp 110A having the ellipsoidal reflector 114A in the
first embodiment. However, in case that the illumination device 100B uses the light
source lamp 110A, a parallelization concave lens is provided between the light source
lamp 110A and the first lens array in order to emit in parallel the collection light emitted
from the light source lamp 110A on the incident surface of the first lens array. Further,
this parallelization concave lens may be integrated with the light source lamp 110A or
may be provided separately.
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In the second embodiment, only the example of the projector 1000B using the three
liquid crystal display devices 400R, 400G, and 400B is given. However, the invention
can be also applied to a projector using only one liquid crystal panel, a projector using two
liquid crystal panels, or a projector using four or more liquid crystal panels.
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In the projectors according to the above embodiments, the illumination device of
the invention is applied to the transmission type projector. However, the invention can be
also applied to a reflection type projector. Here, the "transmission type" means that the
elector-optic modulator as the optical modulation means is a type of transmitting light
such as a transmission type liquid crystal panel, and the "reflection type" means that the
elector-optic modulator as the optical modulation means is a type of reflecting light such
as a reflection type liquid crystal panel. Also in case that the invention is applied to the
reflection type projector, the almost similar effect to the effect in the transmission type
projector can be obtained.
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In the projectors according to the above embodiments, though the liquid crystal
panel is used as the electro-optic modulator, the invention is not limited to this. As long
as the electro-optic modulator modulates generally the incident light according to the
image data, any modulator, for example, a micro-mirror type modulator may be used. As
the micro-mirror type modulator, for example, a DMD (digital micro-mirror device) can
be used.
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In addition, the invention can be also applied to a front projection type projector
which projects a projection image from a viewing side, or a rear projection type projector
which projects a projection image from the opposite side to a viewing side.
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Though the best constitution for embodying the invention has been disclosed in the
above description, the invention is not limited to this. Namely, though the invention has
been shown and described in terms of the specific embodiments, those skilled in the art,
without departing from the technical spirit and the object of the invention, can make
various modifications in the shape, material, number of parts, or other detailed
constitution in the above-described embodiments.
-
Accordingly, the description in which the above-disclosed shape and the material
of parts have been limited is illustrative in order to facilitate understanding of the
invention and not restrictive. Therefore, the descriptions of the parts by their names, a
part or all of limitation of which are released in the shape and material, are included in the
invention.
[Description of Reference Numerals and Signs]
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1000A, 1000B... projector, 2... luminous part, 2is... inner surface of luminous part, 2os...
outer surface of luminous part, 3, 4... seal part, 5, 6... electrode, 7,8... inorganic adhesive,
100A, 100B... Illumination device, 110A, 110B... Light source lamp, 110Aax, 110Bax...
illumination light axis, 112... light emitting tube, 114A... ellipsoidal reflector, 114B...
paraboloidal reflector, 116... auxiliary mirror, 116is... reflection concave surface, 118...
infrared mirror, 120... integrator rod, 140... relay optical system, 150... first lens array,
160... second lens array, 170... polarization converting element, 180... superimposing lens,
200... color separation optical system, 300... relay optical system, 400... liquid crystal
display device, 400R... liquid crystal display device for red color light, 400G... liquid
crystal display device for green color light, 400B... liquid crystal display device for blue
color light, 500... cross dichroic prism, 600... projection optical system, D... radius of
curvature of reflection concave surface 116is, d... distance between center P of luminous
part 2 and center Q of curvature of reflection concave surface 116is, P... center of
luminous part 2, Q... center of curvature of auxiliary mirror 116